Real time resistance monitoring of an arc welding circuit

ABSTRACT

A welding or additive manufacturing power supply includes output circuitry configured to generate a welding waveform, a current sensor for measuring a welding current generated by the output circuitry, a voltage sensor for measuring an output voltage of the welding waveform, and a controller operatively connected to the output circuitry to control the welding waveform, and operatively connected to the current sensor and the voltage sensor to monitor the welding current and the output voltage. A portion of welding waveform includes a controlled change in current from a first level to a second level different from the first level. The controller is configured to determine a circuit inductance from the output voltage and the controlled change in current, and further determine a change in resistance of a consumable electrode in real time based on the circuit inductance.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 62/826,323 filed on Mar. 29, 2019, the disclosureof which is incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to power supplies for generatingelectrical arcs used in welding or welding-type processes, such as metaladditive manufacturing.

Description of Related Art

Welding power supplies can generate complex welding waveforms with veryfast output current changes. Such complex welding waveforms aretypically controlled based on voltage and/or current feedbackmeasurements. The feedback measurements can be made by the welding powersupply, or by a welding wire feeder that is local to the workpiece beingwelded but is more remote from the welding power supply. Long lengths ofwelding cable extending from the power supply can add significantinductance, and thus impedance, to the welding circuit. When longwelding cables are used, the performance of the power supply may belimited, and accurate feedback measurements become more difficult. Thewelding power supply can make remote feedback measurements overdedicated sense leads that extend to the workpiece; however, such senseleads increase system complexity and cost, and tend to be fragile andeasily broken. Thus, the use of sense leads is generally not desired.The welding wire feeder can make the remote feedback measurements;however, measurement data must then be communicated back to the weldingpower supply quickly for it to be of use. Such feedback communicationsrequire additional circuitry and possibly additional control wiringbetween the power supply and wire feeder. The feedback communicationsmay occur over the welding cables, but there tends to be a significantamount of noise along the welding cables which must be accommodated. Itwould be desirable for the welding power supply to accurately determinewelding conditions occurring remotely at the workpiece, in real time,even when the welding circuit includes a significant amount ofinductance due to long cable lengths, without the need for dedicatedsense leads or voltage/current feedback data from the welding wirefeeder.

BRIEF SUMMARY OF THE INVENTION

The following summary presents a simplified summary in order to providea basic understanding of some aspects of the devices, systems and/ormethods discussed herein. This summary is not an extensive overview ofthe devices, systems and/or methods discussed herein. It is not intendedto identify critical elements or to delineate the scope of such devices,systems and/or methods. Its sole purpose is to present some concepts ina simplified form as a prelude to the more detailed description that ispresented later.

In accordance with one aspect of the present invention, provided is awelding or additive manufacturing power supply. The power supplyincludes output circuitry configured to generate a welding waveform, acurrent sensor for measuring a welding current generated by the outputcircuitry, a voltage sensor for measuring an output voltage of thewelding waveform, and a controller operatively connected to the outputcircuitry to control the welding waveform, and operatively connected tothe current sensor and the voltage sensor to monitor the welding currentand the output voltage. A portion of welding waveform includes acontrolled change in current from a first level to a second leveldifferent from the first level. The controller is configured todetermine a circuit inductance from the output voltage and thecontrolled change in current, and further determine a change inresistance of a consumable electrode in real time based on the circuitinductance.

In accordance with another aspect of the present invention, provided isa welding or additive manufacturing system. The system includes aconsumable electrode, a torch, a wire feeder that advances theconsumable electrode through the torch during a deposition operation,and a power supply operatively connected to the wire feeder and thetorch through at least one cable. The power supply is configured toprovide a series of welding waveforms to the torch to generate a weldingcurrent in the consumable electrode. A portion of an individual weldingwaveform of said series of welding waveforms includes a controlledchange in current from a first level to a second level different fromthe first level. The power supply is configured to determine a circuitinductance based on voltage and current measurements made during thecontrolled change in current. The power supply is further configured todetermine a change in resistance of the consumable electrode in realtime based on the circuit inductance.

In accordance with another aspect of the present invention, provided isa welding or additive manufacturing power supply. The power supplyincludes output circuitry configured to generate a welding waveform, acurrent sensor for measuring a welding current generated by the outputcircuitry, a voltage sensor for measuring an output voltage of thewelding waveform, and a controller operatively connected to the outputcircuitry to control the welding waveform, and operatively connected tothe current sensor and the voltage sensor to monitor the welding currentand the output voltage. A portion of welding waveform includes acontrolled change in current from a first level to a second leveldifferent from the first level. The controller is configured todetermine a circuit inductance in real time during a depositionoperation from at least the controlled change in current, and furtherdetermine a change in resistance of a consumable electrode in real timebased on the circuit inductance.

The power supply or controller can be configured to determine a circuitimpedance in real time from the welding current and the output voltage.The controlled change in current can occur during a current ramp portionof the welding waveform. The power supply or the controller can beconfigured to determine clearance of a short circuit event based on thechange in resistance of the consumable electrode. The power supply orthe controller can be configured to determine a change in electrodestickout distance based on the change in resistance of the consumableelectrode. The power supply can include an output switch, and a resistorconnected in parallel with the output switch, and the welding waveformcan include a minimum current portion, a pinch current portion during ashort circuit event between the consumable electrode and a workpiece, aplasma boost pulse portion, and a tail out from the plasma boost pulseportion to a background current level, and the power supply/controllercan be configured to deactivate the output switch to implement theminimum current portion of the welding waveform based on the change inresistance of the consumable electrode. The power supply/controller canbe configured to compare the change in resistance of the consumableelectrode to a threshold value and deactivate the output switch when thechange in resistance of the consumable electrode meets or exceeds thethreshold value. The power supply/controller can be configured tocompare the circuit inductance to a threshold value and controlreactivation of the output switch based on a result of comparing thecircuit inductance to the threshold value. In certain embodiments, thepinch current portion of the welding waveform can include a constantcurrent portion from which the power supply/controller determines abaseline circuit resistance. The power supply/controller can beconfigured to adjust a welding waveform parameter based on the circuitinductance or the baseline circuit resistance. The welding waveformparameter can be a welding current ramp rate and/or an average weldingvoltage.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other aspects of the invention will become apparent tothose skilled in the art to which the invention relates upon reading thefollowing description with reference to the accompanying drawings, inwhich:

FIG. 1 is a perspective view of a welding system;

FIG. 2 is a is a schematic diagram of the welding system;

FIG. 3 is a schematic diagram of the welding system;

FIG. 4 is a schematic diagram of a welding circuit;

FIG. 5 illustrates a welding electrode and workpiece;

FIG. 6 illustrates a welding waveform;

FIG. 7 is a graph of welding circuit impedance;

FIG. 8 is a graph of inductive reactance;

FIG. 9 is a graph of compensated resistance;

FIG. 10 illustrates a welding waveform;

FIG. 11 is a flow diagram; and

FIG. 12 illustrates an example controller.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary embodiments of the invention will now be described below byreference to the attached figures. The described exemplary embodimentsare intended to assist the understanding of the invention, and are notintended to limit the scope of the invention in any way. Like referencenumerals refer to like elements throughout.

As used herein, “at least one”, “one or more”, and “and/or” areopen-ended expressions that are both conjunctive and disjunctive inoperation. For example, each of the expressions “at least one of A, Band C”, “at least one of A, B, or C”, “one or more of A, B, and C”, “oneor more of A, B, or C” and “A, B, and/or C” means A alone, B alone, Calone, A and B together, A and C together, B and C together, or A, B andC together. Any disjunctive word or phrase presenting two or morealternative terms, whether in the description of embodiments, claims, ordrawings, should be understood to contemplate the possibilities ofincluding one of the terms, either of the terms, or both terms. Forexample, the phrase “A or B” should be understood to include thepossibilities of “A” or “B” or “A and B.”

While embodiments of the present invention described herein arediscussed in the context of GMAW type welding, other embodiments of theinvention are not limited thereto. For example, embodiments can beutilized in SAW and FCAW type welding operations, as well as othersimilar types of deposition operations. Further, embodiments of thepresent invention can be used in manual, semi-automatic and roboticwelding operations. Embodiments of the present invention can also beused in metal deposition operations that are similar to welding, such asadditive manufacturing, hardfacing, and cladding. As used herein, theterm “welding” is intended to encompass all of these technologies asthey all involve material deposition to either join or build up aworkpiece. Therefore, in the interests of efficiency, the term “welding”is used below in the description of exemplary embodiments, but isintended to include all of these material deposition operations, whetheror not joining of multiple workpieces occurs.

FIG. 1 illustrates an exemplary embodiment of an arc welding system 100.The system 100 includes a welding power supply 110, a welding wirefeeder 140, a welding wire source 160, a gas source 120, and a weldingtorch or gun 130. The wire feeder 140 includes a controller 150 and awire gripping device 170. The controller 150 may include a motor (notshown) that drives the wire gripping device 170 to pull a welding wireelectrode from the welding wire source 160 (e.g., spool, drum, etc.)through the wire gripping device 170 and into the welding gun 130 via awelding cable 135. Such welding systems are well known in the art. Afirst electrical terminal or output stud of the welding power supply 110may be connected to a workpiece W such that the welding wire electrode,which is electrically connected to a second electrical terminal oroutput stud of the welding power supply, may be applied to the workpieceW via the welding gun 130 to produce a weld in an arc welding operation.

FIG. 2 provides a schematic diagram of the arc welding system 100. Thepower supply 110 provides a welding signal or welding waveform throughwelding leads 103 and 105 to the workpiece W. The welding signal has acurrent and a voltage, and can be a type of welding signal that requiresa change in current from one level to another. For example, the signalcan be a pulse welding signal which changes from a background to a peaklevel during welding, or an alternating polarity waveform that changesfrom one polarity to the other at a known rate. The current from thepower supply 110 is delivered to an electrode 111 via a contact tip 109to generate an arc 114 between the electrode 111 and the workpiece W. Asis common in GMAW welding operations, the positive lead 103 can becoupled to a wire feeder 140 which then passes the welding currentthrough a welding cable 135 to the contact tip 109. In such aconfiguration the overall length of the positive lead 103 is acombination of the connection from the power supply 110 to the wirefeeder 140 and from the wire feeder to the contact tip 109. Of coursethe lead 103 can be coupled directly to the contact tip 109. The powersupply 110 can include terminals or output studs 115, 116 that connectthe welding leads 103, 105 to the electrical output of the power supply.

FIG. 3 provides another schematic diagram of the arc welding system 100with additional details of the power supply 110 illustrated. The powersupply 110 receives electrical energy for generating the arc 114 from apower source 172, such as a commercial power source or a generator. Thepower source 172 can be a single phase or three phase power source. Incertain embodiments, the arc welding system 100 can be a hybrid systemthat includes one or more batteries (not shown) that also supply energyto the welding power supply 110. The power supply 110 includes outputcircuitry for supplying the welding waveforms to the contact tip 109 andelectrode 111. The output circuitry can include a switching type powerconverter such as an inverter 174 for generating the arc 114 accordingto a desired welding waveform. Alternatively or additionally, thewelding power supply could include a DC chopper (not shown) or boostconverter (not shown) for generating welding waveforms. AC power fromthe power source 172 is rectified by an input rectifier 176. The DCoutput from the rectifier 176 is supplied to the inverter 174. Theinverter 174 supplies high-frequency AC power to a transformer 178, andthe output of the transformer is converted back to DC by an outputrectifier 180.

Current from the output circuitry flows to the contact tip 109 and tothe electrode 111 and workpiece W to generate the arc 114. The weldingcurrent from the output rectifier 180 can flow through either acontrollable output switch 182 or a resistor 170. Deactivating theoutput switch 182 will quickly reduce the welding current by forcing itthrough the resistor 170. The output switch 182 and resistor 170 can beused to reduce spatter at specific points during welding by quicklyreducing the welding current. For example, when conducting a surfacetension transfer STT or a short-arc welding operation, the weldingcurrent can be rapidly brought to a low current level when a shortcircuit event between the welding electrode 111 and workpiece W occursand/or is about to break, by selectively deactivating the output switch182. It can be seen that the resistor 170 is connected in parallel withthe output switch 182. When the output switch 182 is in the on oractivated state, the welding current flows through the output switch tothe torch 130 and electrode 111. When in the on state, the output switch182 effectively shorts out the resistor 170. When the output switch 182is in an off or deactivated state, the resistor 170 is connected inseries with the torch 130 and electrode 111, and the welding currentflows through the resistor. In certain embodiments, the resistor 170 canbe adjustable to control the magnitude of the low current level.

The welding torch 130 is operatively connected to the power supply 110.The power supply 110 supplies welding output electrical energy to thewelding torch 130 to generate the arc 114 and perform the depositionoperation (e.g., welding, additive manufacturing, hardfacing, etc.) Thetorch 130 can have a contact tip 109 for transferring the electricalenergy supplied by the power supply 110 to the electrode 111. Theelectrode 111 can be a solid, flux-cored or metal-cored consumable wirewelding electrode. The electrode 111 can be fed from the welding wiresource 160 by the wire feeder 140, which advances the electrode toward aweld puddle during the welding operation. As shown schematically in FIG.3 , the wire feeder 140 can include motor-operated pinch rollers fordriving the electrode 111 toward the torch 130.

The arc welding system 100 can be configured for direct currentelectrode positive (DC+) or “reverse” polarity wherein the contact tip109 and electrode 111 are connected to a positive lead from the powersupply 110, and the workpiece W is connected to a negative lead.Alternatively, the arc welding system 100 can be configured for directcurrent electrode negative (DC−) or “straight” polarity, wherein theworkpiece W is connected to the positive lead and the contact tip 109and electrode 111 are connected to the negative lead. Further, the arcwelding system 100 can be configured for AC welding in which ACwaveforms are provided to the contact tip 109, electrode 111 andworkpiece W.

The power supply 110 includes a controller 184 operatively connected tothe output circuitry, such as to the inverter 174, for controlling thewelding waveforms generated by the power supply. The controller 184 canprovide a waveform control signal to the inverter 174 to control itsoutput. The controller 184 controls the output of the inverter 174 viathe waveform control signal, to achieve a desired welding waveform,welding voltage, welding current, etc. The waveform control signal cancomprise a plurality of separate control signals for controlling theoperation of various switches (e.g., transistor switches) within theinverter 174. The controller 184 is also operatively connected to theoutput switch 182 to control its switching operations between the on,activated state and the off, deactivated state. The controller 184monitors aspects of the welding process via feedback signals. Forexample, a current sensor 186, such as a current transformer (CT) orshunt, can provide a welding current feedback signal to the controller184, and a voltage sensor 188 can provide a welding voltage feedbacksignal to the controller. The current sensor 186 and voltage sensor 188are located at the power supply 110, which may be remote from theworkpiece W and arc 114. However, as will be discussed further below,the controller 184 can monitor conditions of the welding process, and inparticular conditions occurring remotely at the workpiece W, fromvoltage and current measurements made at the output studs 115, 116 ofpower supply 110 by the voltage and current sensors.

The controller 184 can be an electronic controller and may include aprocessor. The controller 184 can include one or more of amicroprocessor, a microcontroller, a digital signal processor (DSP), anapplication specific integrated circuit (ASIC), a field-programmablegate array (FPGA), discrete logic circuitry, or the like. The controller184 can include a memory portion (e.g., RAM or ROM) storing programinstructions that cause the controller to provide the functionalityascribed to it herein. The controller 184 can include a plurality ofphysically separate circuits or electronic devices, such as a processorin combination with separate comparators, logic circuits, etc. However,for ease of explanation, the controller 184 is shown as a monolithicdevice.

With reference to FIGS. 2 and 3 , the welding leads 103 and 105 can bequite long as the workpiece W can be positioned far away from the powersupply 110. For example, in some instances the leads 103/105 can have alength of 100 feet or longer. Such long cable lengths can significantlyincrease the inductance of the welding circuit and negatively affect theability of the power supply 110 to determine the conditions at theworkpiece, such as the arc voltage, electrode “stickout” length from thecontact tip, arc length, whether a short circuit is about to clear, etc.The conditions at the workpiece may require adjustments to be made tothe welding waveform or to other welding parameters, and the ability ofthe power supply to timely and correctly make such adjustments can beimpaired by long cable lengths. For example, a large cable inductance(e.g., 35 μH or greater) can negatively affect the ability of the powersupply 110 to determine if a short circuit between the electrode 111 andworkpiece W is about to clear, to determine changes to electrode“stickout”, to determine welding path adjustments during through-arcseam tracking (TAST), etc. Further, it may be desirable to adjust somewelding parameters when the inductance and/or resistance of the weldingcircuit is large. Examples of such parameters include the average outputvoltage or a “trim” setting on the welding power supply 110, or ramprates of a welding current waveform. If the welding cables are long, thecorresponding increase in inductance and resistance in the weldingcircuit may be accommodated or offset by increasing the average weldingvoltage (e.g., increasing the trim setting) to maintain a proper arclength and energy level supplied to the weld. Welding current ramp ratescan be reduced when the welding cables are long. In more extremecircumstances, if the welding cables are too long or add too muchinductance to the welding circuit, such as when the cables are long andcoiled, it can be desirable to instruct an operator to take remedialaction via an alarm. The power supply 110 discussed herein can determinethe conditions at the workpiece from measurements made remotely at thepower supply, taking into account the inductance of the welding circuit.In certain embodiments, the power supply 110 can determine cableinductance prior to or during welding, and determine the total impedanceand the inductive reactance of the welding circuit in real time. Usingthis information, the power supply 110 can transform the total impedanceof the welding circuit into a compensated resistance that includes theresistance of the welding electrode at the workpiece. The power supply110 can then use the compensated resistance to determine conditions atthe workpiece in real time, such as the point in time when a shortcircuit between the electrode and workpiece is about to clear, andrespond to such conditions (e.g., by reducing the welding current tominimize spatter). Further, the power supply 110 can use the measured orestimated cable inductance and/or compensated resistance to, among otherthings, make parameter adjustments, perform seam tracking, determine theamount of power supplied to the arc, help classify weld quality,generate various alarms, etc.

FIG. 4 shows a schematic diagram of a welding circuit 200. The weldingcircuit 200 extends from the output studs 115, 116 of the power supply110 to the torch and workpiece (not shown). The power supply 110 canmeasure the welding current I_(S) in the welding circuit 200, and theoutput voltage of the welding waveform V_(S) across the output studs115, 116, using the current and voltage sensors in the power supply. Theresistance R_(T) is the resistance at the torch and workpiece, and thevoltage V_(T) is the voltage between the torch and the workpiece. Duringan arc condition, V_(T) is relatively high. However, during a shortcircuit condition between the wire electrode and the workpiece, V_(T) isnearly 0V and is merely the voltage drop across the wire electrode thatis shorted to the workpiece.

The inductance L_(C) is the welding circuit inductance, which includesthe variable cable inductance and also inductances in the power supply.The resistance R_(C) is primarily the resistance of the welding cableand the resistance of the return or ground path, which may be throughthe welding cable or through another return path (e.g., earth ground).The inductance L_(C) and resistance R_(C) will increase with cablelength, and L_(C) can change with cable orientation (e.g., coiled,uncoiled, etc.) Circuit capacitance, or capacitive reactance, cangenerally be ignored as an insignificant contributor to the overallcircuit impedance. When the cable length is short, the measurement ofV_(S) at the power supply 110 can provide useful information aboutconditions at the workpiece, such as whether a short between the weldingelectrode and workpiece is about to occur or clear. However, with longcable lengths and high cable inductances (e.g., 35 μH or greater), theimpedance of the cable dominates the welding circuit, and certainconditions at the workpiece could not conventionally be accuratelyderived from V_(S) and/or I_(S). Thus, dedicated sense leads have beenused by the power supply 110 to monitor V_(T) more directly, but the useof sense leads is generally undesirable for various reasons discussedabove.

The power supply 110, and in particular its controller, is configured toremotely determine conditions at the workpiece by monitoring the weldingcurrent I_(S) and the voltage V_(S) across the output studs 115, 116.The controller can calculate the impedance of the welding circuit,Z_(S), in real time during a welding operation from the equation:Z_(S)=V_(S)/I_(S). Z_(S) is the sum of individual impedances in thewelding circuit, including an inductive reactance X_(C) due to the cableinductance L_(C), the cable resistance R_(C), and the resistance at thetorch/workpiece R_(T). Thus, Z_(S)=X_(C)+R_(C)+R_(T). The inductivereactance, X_(C), is equal to the cable inductance times the rate ofchange of the welding current I_(S) divided by I_(S):X_(C)=(L_(C))(dI_(S)/dt)/I_(S). Substituting for X_(C) in the weldingcircuit impedance equation yields:Z_(S)=(L_(C))(dI_(S)/dt)/I_(S)+R_(C)+R_(T). Thus, the resistance at thetorch/workpiece, R_(T), can be calculated using the following equation:R_(T)=Z_(S)−(L_(C))(dI_(S)/dt)/I_(S)−R_(C). Further, replacing Z_(S)with V_(S)/I_(S) provides the following:R_(T)=V_(S)/I_(S)−(L_(C))(dI_(S)/dt)/I_(S)−R_(C). The calculatedresistance at the torch/workpiece R_(T) can be considered a “compensatedresistance” because the impact of the cable impedance is compensatedfor.

Knowing the resistance R_(T) at the torch/workpiece in real time and/ormonitoring its changes in real time during welding can provide thewelding power supply 110 with important feedback information about whatis occurring at the welding electrode. For example, as a short circuitbetween the welding electrode 111 and the workpiece W is about to clearor break, the electrode exhibits necking or narrowing at the molten weldpuddle 202 (FIG. 5 ). The narrowing of the electrode results in theresistance R_(T) rising. Monitoring the change in R_(T) (e.g., ΔR_(T))can allow the power supply 110 to determine when the short is about toclear, and reduce the welding current (e.g., by deactivating the outputswitch 182—FIG. 3 ), to minimize spatter when the short breaks and anarc reignites. Monitoring R_(T) and/or ΔR_(T) can also provide thewelding power supply 110 with information about changes to electrodestickout, which can be useful when performing through-arc seam tracking.Monitoring R_(T) and/or ΔR_(T) can also provide the welding power supply110 with information about the amount of power or energy delivered tothe workpiece, from which weld quality may be determined.

As noted above, R_(T) can be calculated or estimated using the followingequation: R_(T)=V_(S)/I_(S)−(L_(C))(dI_(S)/dt)/I_(S)−R_(C). The powersupply 110 can monitor V_(S) and I_(S) in real time. To estimate thecircuit inductance L_(C), the power supply can monitor V_(S) while thecurrent is changed in a controlled fashion from a first level to asecond level different from the first level. The controlled currentchange can be a generally linear ramp, or a nonlinear change (e.g., anexponential current change). The controlled current change from thefirst level to the second level can be either positive (e.g., anincreasing current) or negative (e.g., a decreasing current). Further,the controlled current change from the first level to the second levelcan occur while the electrode 111 shorted to the workpiece W. The linearor nonlinear current ramping can be an upward ramp or a downward,decaying ramp, and may occur during active welding or during a weldcable test prior to welding. In certain embodiments, the inductanceL_(C) can be determined repeatedly during welding (e.g., in real time)to account for changes to the circuit inductance over time, due to thewelding cable becoming coiled for example. The cable resistance R_(C)can also be measured during active welding, or during a weld cable test,with the electrode 111 shorted to the workpiece, when the current I_(S)is constant (e.g., dI_(S)/dt=0 to minimize the reactive impedance). Thecircuit inductance L_(C) and resistance R_(C) are preferably measuredwhen the electrode 111 is known to not be necking or narrowing, during asolid short, to provide a baseline circuit impedance. The circuitinductance L_(C) and resistance R_(C) can be measured with the electrode111 shorted to the workpiece W so that a voltage drop across anelectrical arc at the workpiece is eliminated. However, it is to beappreciated that such measurements could be made at other points in timeduring welding, such as when a short is clearing and the welding currentis intentionally rapidly reduced to minimize spatter, or when a pulsecurrent is applied to reestablish an arc following a short circuitevent. Either of these events (e.g., rapidly reducing the current orapplying a current pulse) will include a high magnitude dI_(S)/dt, whichis convenient for calculating the circuit inductance L_(C). The circuitinductance L_(C) and/or resistance R_(C) can be measured during previousdeposition operations and saved in a memory for use during a subsequentdeposition operation, and the values of L_(C) and R_(C) can be updatedfrom time to time as necessary.

In certain embodiments, the effect of the cable resistance R_(C) on thecalculation of R_(T) can be approximated by a calibration variable CV.The calibration variable can be determined empirically and can be storedin a memory of the power supply 110. If a calibration variable is used,the equation for calculating R_(T) will be as follows:R_(T)=Z_(S)−X_(C)−CV=V_(S)/I_(S)−(L_(C))(dI_(S)/dt)/I_(S)CV.

An example calculation and use of the compensated resistance R_(T) willbe discussed in the context of an STT welding operation. A waveformsuitable for STT welding is shown in FIG. 6 , and will be discussed withrespect to system components shown in FIG. 3 . The waveform includes abackground current portion 300, a pinch current portion 302, and aplasma boost pulse 304 followed by a tail out 306 to another backgroundcurrent portion 300. Between the background current portion 300 and thepinch current portion 302, and between the pinch current portion 302 andthe plasma boost pulse 304, are minimum current portions 308 a, 308 b.It can be seen that the background current portion 300 has a greatermagnitude than the minimum current portions 308 a, 308 b, but less thanthe pinch current portion 302 and the plasma boost pulse 304. The outputswitch 182 is in the on state during the background current 300, pinchcurrent 302 and plasma boost pulse 304 portions of the welding waveform,and the welding current flows through the output switch during theseportions. The output switch 182 is in the off state during the minimumcurrent portions 308 a, 308 b, and the welding current flows through theresistor 170 during the minimum current portions. The magnitude of theminimum current portions 308 a, 308 b is determined by the resistancelevel of the resistor 170. An example current range for the backgroundcurrent portion 300 is 15 A to 150 A. An example current range for thepinch current portion 302 and the plasma boost pulse 304 is 150 A to 500A. An example current range for the minimum current portions 308 a, 308b is 20 A to 125 A.

During the background current portion 300, a molten ball forms on theend of the electrode 111, and the electrode can short to the weld puddleon the workpiece W. The controller 184 can recognize the existence ofthe short by monitoring the welding voltage V_(S). When a short isdetected, the controller implements first the minimum current portion308 a and quickly reduces the welding current to the minimum currentlevel 308 a by turning off the output switch 182. Reducing the weldingcurrent helps to ensure a solid short and avoids blowing apart theelectrode like a fuse. After the first minimum current portion 308 a andduring a solid short between the electrode and workpiece, a pinchcurrent 302 is applied through the output switch 182 to neck down theend of the electrode 111 for separation into the weld puddle. Justbefore the short is cleared, at point C on the waveform, the controlleragain turns off the output switch 182 to implement the second minimumcurrent portion 308 b and quickly reduces the welding current to the lowcurrent level to prevent spatter when the molten ball pinches off of theelectrode. When the arc is reestablished, the controller 184 applies apeak current or plasma boost pulse 304 through the output switch 182, toset the proper arc length and push the weld puddle away from the wireelectrode 111. The plasma boost pulse 304 is then tailed out 306 by thecontroller 184, to return the welding current to the background current300 level.

At point C on the waveform, the molten ball is about to pinch off fromthe electrode 111, and the electrode is necking as shown in FIG. 5 . Thereduced cross-sectional area across the electrode 111 due to the neckingcauses the resistance R_(T) at the torch to rise. By monitoring thechange in value of R_(T) (e.g., ΔR_(T)) in real time, from a point priorin time to necking of the electrode 111 until point C, the controller184 can determine when pinch off is about to occur and when the shortcircuit event will clear. When the controller 184 determines that pinchoff is about to occur, based on the increased resistance of R_(T), itdeactivates the output switch 182 to reduce the current to the minimumcurrent level 308 b. In certain embodiments, the change in value ofR_(T), ΔR_(T), can be compared to a threshold value to determine whenpinch off is about to occur such that when ΔR_(T) meets or exceeds thethreshold, the controller 184 deactivates the output switch 182. Thethreshold value of ΔR_(T) is indicative of the molten ball about topinch off from the electrode 111, and can be determined empirically andbe stored in a memory of the power supply 110. Example ranges for thethreshold value of ΔR_(T) are 1-10 mohm, 2-5 mohm, etc., however, otherranges are possible and can be determined empirically.

In conventional STT welding, the pinch current portion of the weldingwaveform is a substantially linear current ramp from a first currentlevel to a second current level. However, the pinch current portion 302of the waveform in FIG. 6 is configured to allow the circuit inductanceL_(C) and baseline circuit resistance R_(C) to be determined in realtime during welding based on voltage and/or current measurements madewhile the welding electrode is solidly shorted to the workpiece. Thereal time circuit inductance L_(C) and resistance R_(C) measurements canthen be used to calculate the compensated resistance R_(T) of theelectrode at the workpiece during a final current ramp of the pinchcurrent portion 302 while the electrode necks down. The pinch currentportion 302 has a first linear ramp 309 (period A) that provides acontrolled change in current level (e.g., from a first level to a secondlevel) at constant rate of change of the current (dI_(S)/dt). Thecircuit inductance L_(C) can be calculated during the first linear ramp309 from the output voltage of the welding waveform measured at thepower supply and the change in current. The first linear ramp 309 isfollowed by a constant current portion 310 during which the reactiveimpedance due to circuit inductance is minimized. The cable or baselinecircuit resistance R_(C) can be calculated during the constant currentportion 310 of the pinch current 302 (e.g., during period B). During thefirst linear ramp 309 and constant current portion 310 of the pinchcurrent 302, the electrode is heated but has not yet pinched off ornecked down significantly. Pinching occurs during a second ramp 312,which can have the same slope as the first linear ramp 309 or adifferent slope. The controller 184 monitors the change in the value ofR_(T) (ΔR_(T)) during the second ramp 312, from a baseline or offsetresistance R_(C) measured during the constant current portion 310, topredict when the molten ball is about to pinch off, in order to properlytime the deactivation of the output switch 182 and quickly reduce thewelding current I_(S). Conventionally, operation of the output switch182 was based on the rate of change of voltage at the workpiecedetermined using sense leads or communicated by the wire feeder.However, monitoring changes in the compensated resistance R_(T) asdescribed above and operating the output switch 182 based thereoneliminates the need for the additional sense leads and communicationsfrom the wire feeder. It is to be appreciated that the circuitinductance L_(C) can be determined from portions of the welding waveformother than the pinch current portion 302. For example, the circuitinductance L_(C) can be determined from the decrease in current from endof the pinch current portion (point C) to the minimum current portion308 b, or from the increase in current from the end of the minimumcurrent portion 308 b to the plasma boost pulse 304. Further, thecircuit inductance L_(C) can be determined from the energy appliedduring welding and the welding current, while the current isincreased/decreased linearly or nonlinearly.

FIGS. 7-9 graphically show how the impedance of the welding circuitZ_(S) as measured at the welding power supply, the inductive reactanceof the welding circuit X_(C), and the compensated resistance R_(T)behave while the electrode is necking during pinch off. The behavioroccurs during the second ramp 312 portion of the example currentwaveform shown in FIG. 6 , as the power supply monitors ΔR_(T) todetermine the impending pinch off of the molten ball from the electrode.It can be seen in FIG. 7 that the impedance Z_(S) remains relativestable while the current I_(S) is ramped upward to pinch off the moltenball. Thus, Z_(S) alone does not provide a good indication of theimpending separation of the molten ball. The inductive reactance X_(C)(FIG. 8 ) is sloped linearly downward as the current I_(S) is rampedupward. Because X_(C)=(L_(C))(dI_(S)/dt)/I_(S), when I_(S) ramped upwardduring the second ramp 312 portion, the inductive reactance X_(C)decreases linearly. The compensated resistance R_(T) increases generallylinearly while the electrode is necking, as shown in FIG. 9 . Bymonitoring the change in R_(T), the power supply can predict when themolten ball will pinch off and respond accordingly by reducing thewelding current.

FIG. 10 shows an example welding waveform similar to FIG. 6 . As thewelding cable length and inductance level of the welding circuitincreases, the ability of the power supply to accurately determine whenthe molten ball will pinch off from the electrode can decrease. That is,the power supply's determination of the compensated resistance R_(T) canbecome less accurate with increasing cable length/inductance. Undernormal conditions wherein the compensated resistance R_(T) can beaccurately determined, the power supply will deactivate the outputswitch 182 (FIG. 3 ) for a period of time to allow the arc toreestablish. However, if the output switch 182 is deactivated too early(e.g., due to an inaccurate calculation of R_(T)), before the moltenball is ready to detach, it may not detach properly, which can result inelectrode stubbing. The power supply is more likely to deactivate theoutput switch 182 too early when the cable inductance and circuitinductance L_(C) are large because its determination of the compensatedresistance R_(T) is less accurate. To account for the possibility thatthe calculation of R_(T) is not accurate, and that the output switch 182will be deactivated too early, before the molten ball is ready to pinchoff, the power supply can reactivate or turn on the output switch 182sooner than it normally would. This will increase the welding currentduring pinch off, which may result in more spatter, but it will help toensure separation of the molten ball and prevent stubbing of theelectrode. In an example embodiment, the power supply compares themeasured or estimated circuit inductance L_(C) to a threshold level orvalue (e.g., 35 μH, 40 μH, 50 μH, greater than 50 μH, etc.) When thecircuit inductance L_(C) meets or exceeds the threshold, the powersupply reactivates the output switch 182 when a predetermined currentlevel D below the pinch current is reached, after deactivating theoutput switch at point C. The predetermined current level D is higherthan the level of the minimum current portion 308 b that is normallydelivered to the welding electrode while the short circuit clears. Anexample current range for the predetermined current level D is 40 A to125 A. When the welding current drops to the predetermined current levelD, the power supply reactivates the output switch 182 and controls thewelding current. The predetermined current level D can be a levelsufficient to clear the short and can be determined empirically. Thepower supply can control the welding current to maintain a constantlevel (e.g., level D), or be ramped (e.g., ramped downward), prior toapplying the plasma boost pulse 304.

Occasionally during the tail out 306, a very brief short circuit betweenthe electrode and the workpiece can occur, which quickly clears. Thepower supply may recognize the existence of the short circuit andimproperly deactivate the output switch 182 to reduce the current. Thisis shown at point E in FIG. 10 , wherein the output switch has beendeactivated and the current level reduced. Because the short occurredduring the tail out 306 to the background current portion 300, after theoutput switch is reactivated, the power supply would tend to control thecurrent to the background level 300. However, in such a scenario, lessenergy and heat are delivered to the electrode during the tail out 306and background current 300 portions than is desired (which can result inpoor droplet separation), because a portion of the tail out has beenremoved. To address this problem, the power supply (e.g., thecontroller) can include a buffer that stores a running memory of thecurrent level. The running memory can be any length of time as desired,such as from less than a second to several minutes, for example. Thepower supply can then return to a previous current level stored in therunning memory, after the output switch is reactivated, as shown in FIG.10 . Returning to the current level that was reached prior todeactivation of the output switch can result in slightly extending thelength of the tail out 306 and background portion 300 for one period ofthe waveform. Various parameters can be stored in a running memory ofthe power supply, such as voltage, power, impedance, compensatedresistance, etc.

Determining electrode necking and molten ball pinch off is just oneexample application of the above-discussed measurements and calculationsconcerning welding circuit impedances. The compensated resistance R_(T)could also be used to determine changes in electrode stickout, such aswhen automatically seam tracking during welding. The welding electrodehas a substantially smaller cross section, and can have a higherresistance, than the welding cables. The resistance of the weldingelectrode will decrease as the stickout decreases. Monitoring changes toelectrode stickout using the compensated resistance R_(T) can help toimprove the accuracy of seam tracking, or any other process that isbased on stickout or during which stickout is monitored. Analyzing thecompensated resistance R_(T) can also provide information about theamount of power or energy delivered to the workpiece, from which weldquality may be determined. The weld quality could be further classifiedaccording to the shielding gas mixture used during welding. For example,if the resistance or impedance of the welding circuit is outside of anacceptable range for a given electrode, gas and contact tip to workdistance (CTWD), an appropriate alarm could be generated or the weldflagged as being out of specification. The measured circuit inductanceand resistance (e.g., baseline circuit resistance and/or compensatedresistance) could be used to automatically make adjustments to weldingparameters, such as the welding voltage, or to generate alarms or otherwarnings. As noted above, a “trim” setting of the power supply can beadjusted based on the cable resistance. The trim setting is an overallvoltage adjustment to control arc length. When the welding cableresistance is high, the power supply can increase the trim toaccommodate the increased voltage drop across the weld cables. Thewelding power supply could include a lookup table that relates cableresistance and welding current to trim values, to automatically adjustthe trim setting to an appropriate value for the current welding systemsetup.

FIG. 11 is a flow diagram of an example process performed by a weldingpower supply. In step 350, the power supply provides a series of weldingwaveforms to a consumable electrode. From data obtained prior to orduring the provision of the welding waveforms to the electrode, thepower supply determines a circuit inductance of a welding circuit (step352). The circuit inductance determination can be based on voltage andcurrent measurements made while the current level through the electrodeis changed in a controlled manner. The power supply further determines abaseline resistance of the welding circuit (step 354). The resistancedetermination can be based on voltage and current measurements madewhile the current level through the electrode is held constant and theelectrode is shorted to the workpiece. The inductance and resistancemeasurements can be made in real time during a welding or otherdeposition operation. The power supply can further determine animpedance of the welding circuit in real time from voltage and currentmeasurements made during the deposition operation (step 356). From theimpedance of the welding circuit, real time voltage and currentmeasurements, the circuit inductance and the baseline resistance, thepower supply can determine a change in a compensated resistance (e.g.,due to electrode necking) in the welding circuit in real time (step358). For example, the power supply can transform the total impedance ofthe welding circuit into a compensated resistance. Based on the changein the compensated resistance, the power supply recognize that a shortcircuit condition is about to clear and can control operations of anoutput switch to reduce/minimize the welding current and minimizespatter during the deposition operation (step 360).

FIG. 12 illustrates an embodiment of an example controller 184 of thewelding power supply. The controller 184 includes at least one processor414 which communicates with a number of peripheral devices via bussubsystem 412. These peripheral devices may include a storage subsystem424, including, for example, a memory subsystem 428 and a file storagesubsystem 426, user interface input devices 422, user interface outputdevices 420, and a network interface subsystem 416. The input and outputdevices allow user interaction with the controller 184. Networkinterface subsystem 416 provides an interface to outside networks and iscoupled to corresponding interface devices in other computer systems.

User interface input devices 422 may include a keyboard, pointingdevices such as a mouse, trackball, touchpad, or graphics tablet, ascanner, a touchscreen incorporated into the display, audio inputdevices such as voice recognition systems, microphones, and/or othertypes of input devices. In general, use of the term “input device” isintended to include all possible types of devices and ways to inputinformation into the controller 184 or onto a communication network.

User interface output devices 420 may include a display subsystem, aprinter, a fax machine, or non-visual displays such as audio outputdevices. The display subsystem may include a cathode ray tube (CRT), aflat-panel device such as a liquid crystal display (LCD), a projectiondevice, or some other mechanism for creating a visible image. Thedisplay subsystem may also provide non-visual display such as via audiooutput devices. In general, use of the term “output device” is intendedto include all possible types of devices and ways to output informationfrom the controller 184 to the user or to another machine or computersystem.

Storage subsystem 424 provides a non-transitory, computer-readablestorage medium that stores programming and data constructs that providethe functionality of some or all of the control algorithms and softwaremodules described herein. These software modules are generally executedby processor 414 alone or in combination with other processors. Memory428 used in the storage subsystem can include a number of memoriesincluding a main random access memory (RAM) 430 for storage ofinstructions and data during program execution and a read only memory(ROM) 432 in which fixed instructions are stored. A file storagesubsystem 426 can provide persistent storage for program and data files,and may include a hard disk drive, a floppy disk drive along withassociated removable media, a CD-ROM drive, an optical drive, orremovable media cartridges. The modules implementing the functionalityof certain embodiments may be stored by file storage subsystem 426 inthe storage subsystem 424, or in other machines accessible by theprocessor(s) 414.

Bus subsystem 412 provides a mechanism for letting the variouscomponents and subsystems of the controller 184 communicate with eachother as intended. Although bus subsystem 412 is shown schematically asa single bus, alternative embodiments of the bus subsystem may usemultiple buses.

Many other configurations of the controller 184 are possible having moreor fewer components than the controller depicted in FIG. 12 .

It should be evident that this disclosure is by way of example and thatvarious changes may be made by adding, modifying or eliminating detailswithout departing from the fair scope of the teaching contained in thisdisclosure. The invention is therefore not limited to particular detailsof this disclosure except to the extent that the following claims arenecessarily so limited.

What is claimed is:
 1. A welding or additive manufacturing power supply,comprising: output circuitry configured to generate a welding waveform,wherein the output circuitry includes at least one of an inverter and aDC chopper; a current sensor for measuring a welding current generatedby the output circuitry; a voltage sensor for measuring an outputvoltage of the welding waveform; and a controller operatively connectedto the output circuitry to control the welding waveform, and operativelyconnected to the current sensor and the voltage sensor to monitor thewelding current and the output voltage, wherein a portion of weldingwaveform includes a controlled change in current, from a first level toa second level different from the first level, during a short circuitevent between a consumable wire electrode and a workpiece, and whereinthe controller is configured to calculate a circuit inductance valuethat includes a variable cable inductance level from the output voltageand the controlled change in current, and further calculate a change inresistance of the consumable wire electrode in real time from thecircuit inductance value.
 2. The welding or additive manufacturing powersupply of claim 1, wherein the controller is configured to determine acircuit impedance in real time from the welding current and the outputvoltage.
 3. The welding or additive manufacturing power supply of claim1, wherein the controlled change in current occurs during a current rampportion of the welding waveform.
 4. The welding or additivemanufacturing power supply of claim 1, wherein the controller isconfigured to determine clearance of the short circuit event based onthe calculated change in resistance of the consumable wire electrode. 5.The welding or additive manufacturing power supply of claim 1, whereinthe controller is configured to determine a change in electrode stickoutdistance based on the calculated change in resistance of the consumablewire electrode.
 6. The welding or additive manufacturing power supply ofclaim 1, further comprising: an output switch; and a resistor connectedin parallel with the output switch, wherein the welding waveformincludes a minimum current portion, a pinch current portion during theshort circuit event between the consumable wire electrode and theworkpiece, a plasma boost pulse portion, and a tail out from the plasmaboost pulse portion to a background current level, and wherein thecontroller is operatively connected to the output switch and isconfigured to deactivate the output switch to implement the minimumcurrent portion of the welding waveform based on the calculated changein resistance of the consumable wire electrode.
 7. The welding oradditive manufacturing power supply of claim 6, wherein the controlleris configured to compare the calculated change in resistance of theconsumable wire electrode to a threshold value and deactivate the outputswitch when the calculated change in resistance of the consumable wireelectrode meets or exceeds the threshold value.
 8. The welding oradditive manufacturing power supply of claim 6, wherein the controlleris configured to compare the circuit inductance value to a thresholdvalue and control reactivation of the output switch based on a result ofcomparing the circuit inductance value to the threshold value.
 9. Thewelding or additive manufacturing power supply of claim 6, wherein thepinch current portion includes a constant current portion that minimizesreactive impedance, and wherein the controller calculates a baselinecircuit resistance from the constant current portion during minimizedreactive impedance.
 10. The welding or additive manufacturing powersupply of claim 1, wherein the controller is configured to adjust awelding current ramp rate based on the circuit inductance value.
 11. Awelding or additive manufacturing system, comprising: a consumable wireelectrode; a torch; a wire feeder that advances the consumable wireelectrode through the torch during a deposition operation; and a powersupply operatively connected to the wire feeder and the torch through atleast one cable, wherein the power supply is configured to provide aseries of welding waveforms to the torch to generate a welding currentin the consumable wire electrode, wherein a portion of an individualwelding waveform of said series of welding waveforms includes acontrolled change in current from a first level to a second leveldifferent from the first level during a short circuit event between theconsumable wire electrode and a workpiece, and wherein the power supplyis configured to calculate a circuit inductance value that includes avariable inductance level of the at least one cable from voltage andcurrent measurements made during the controlled change in current, andwherein the power supply is further configured to calculate a change inresistance of the consumable wire electrode in real time from thecircuit inductance value.
 12. The welding or additive manufacturingsystem of claim 11, wherein the power supply includes a current sensorfor measuring the welding current, and a voltage sensor for measuring anoutput voltage of the power supply, and wherein the power supply isconfigured to determine a circuit impedance in real time from thewelding current and the output voltage.
 13. The welding or additivemanufacturing system of claim 11, wherein the controlled change incurrent occurs during a current ramp portion of the individual weldingwaveform.
 14. The welding or additive manufacturing system of claim 11,wherein the power supply is configured to determine clearance of theshort circuit event based on the calculated change in resistance of theconsumable wire electrode.
 15. The welding or additive manufacturingsystem of claim 11, wherein the power supply is configured to determinea change in electrode stickout distance based on the calculated changein resistance of the consumable wire electrode.
 16. The welding oradditive manufacturing system of claim 11, wherein the power supplycomprises: an output switch; and a resistor connected in parallel withthe output switch, wherein the individual welding waveform includes aminimum current portion, a pinch current portion during the shortcircuit event between the consumable wire electrode and the workpiece, aplasma boost pulse portion, and a tail out from the plasma boost pulseportion to a background current level, and the power supply isconfigured to deactivate the output switch based on the calculatedchange in resistance of the consumable wire electrode.
 17. The weldingor additive manufacturing system of claim 16, wherein the power supplyis configured to compare the calculated change in resistance of theconsumable wire electrode to a threshold value and deactivate the outputswitch when the calculated change in resistance of the consumable wireelectrode meets or exceeds the threshold value.
 18. The welding oradditive manufacturing system of claim 16, wherein the power supply isconfigured to compare the circuit inductance value to a threshold valueand control reactivation of the output switch based on a result ofcomparing the circuit inductance value to the threshold value.
 19. Thewelding or additive manufacturing system of claim 16, wherein the pinchcurrent portion includes a constant current portion that minimizesreactive impedance, and wherein the power supply calculates a baselinecircuit resistance from the constant current portion during minimizedreactive impedance.
 20. The welding or additive manufacturing system ofclaim 11, wherein the power supply is configured to adjust a weldingcurrent ramp rate based on the circuit inductance value.
 21. A weldingor additive manufacturing power supply, comprising: output circuitryconfigured to generate a welding waveform, wherein the output circuitryincludes at least one of an inverter and a DC chopper; a current sensorfor measuring a welding current generated by the output circuitry; avoltage sensor for measuring an output voltage of the welding waveform;and a controller operatively connected to the output circuitry tocontrol the welding waveform, and operatively connected to the currentsensor and the voltage sensor to monitor the welding current and theoutput voltage, wherein a portion of welding waveform includes acontrolled change in current from a first level to a second leveldifferent from the first level, during a short circuit event between aconsumable wire electrode and a workpiece, and wherein the controller isconfigured to calculate a circuit inductance value that includes avariable cable inductance level in real time during a depositionoperation from at least the controlled change in current, and furthercalculate a change in resistance of the consumable wire electrode inreal time from on the circuit inductance value.
 22. The welding oradditive manufacturing power supply of claim 21, wherein the controlleris configured to determine a circuit impedance in real time from thewelding current and the output voltage.
 23. The welding or additivemanufacturing power supply of claim 21, wherein the controlled change incurrent occurs during a current ramp portion of the welding waveform.24. The welding or additive manufacturing power supply of claim 21,wherein the controller is configured to determine clearance of the shortcircuit event based on the calculated change in resistance of theconsumable wire electrode.
 25. The welding or additive manufacturingpower supply of claim 21, wherein the controller is configured todetermine a change in electrode stickout distance based on thecalculated change in resistance of the consumable wire electrode. 26.The welding or additive manufacturing power supply of claim 21, furthercomprising: an output switch; and a resistor connected in parallel withthe output switch, wherein the welding waveform includes a minimumcurrent portion, a pinch current portion during the short circuit eventbetween the consumable wire electrode and the workpiece, a plasma boostpulse portion, and a tail out from the plasma boost pulse portion to abackground current level, and wherein the controller is operativelyconnected to the output switch and is configured to deactivate theoutput switch to implement the minimum current portion of the weldingwaveform based on the calculated change in resistance of the consumablewire electrode.
 27. The welding or additive manufacturing power supplyof claim 26, wherein the controller is configured to compare thecalculated change in resistance of the consumable wire electrode to athreshold value and deactivate the output switch when the calculatedchange in resistance of the consumable wire electrode meets or exceedsthe threshold value.
 28. The welding or additive manufacturing powersupply of claim 26, wherein the controller is configured to compare thecircuit inductance value to a threshold value and control reactivationof the output switch based on a result of comparing the circuitinductance value to the threshold value.
 29. The welding or additivemanufacturing power supply of claim 26, wherein the pinch currentportion includes a constant current portion that minimizes reactiveimpedance, and wherein the controller calculates a baseline circuitresistance from the constant current portion during minimized reactiveimpedance.
 30. The welding or additive manufacturing power supply ofclaim 21, wherein the controller is configured to adjust a weldingcurrent ramp rate based on the circuit inductance value.